Withdrawal and straightening apparatus for continuous casting

ABSTRACT

In a withdrawal and straightening apparatus for continuous casting machines, banks of withdrawal and straightening rolls are mounted above and below the casting, the rolls of each bank being mounted in tiltable yokes which adjust themselves to the curvature of the casting and distribute the loads on the rolls. The rolls of the upper bank are adjustable by hydraulic means connected to the yokes to accommodate castings of different thickness.

United States Patent Burkhardt et al.

[54] WITHDRAWAL AND STRAIGHTENING APPARATUS FOR CONTINUOUS CASTINGInventors: Max Burkhardt, Zurich, Switzerland; Horst Huber, RosellePark, N.J.; Christian Chateau, Saint- Chamond, France Concast AG,Zurich, Switzerland; Concast Incorporated, New York, N.Y.

Filed: May 20,1970

Appl. No.: 38,977

Assignees:

[30] Foreign Application Priority Data May 20, 1969 Switzerland..7645/69 US. Cl ..164/282, 72/160 Int. Cl. ..B22d 11/12 Field of Search..164/82, 282, 283; 72/160, 163,

' [4 1 Dec. 26, 1972 [56] References Cited UNITEDSTATES PATENTS3,257,691 4 6/l966 Krueger ..l64/282 X 3,270,376 9/1966 Thalmann..164/282 X FOREIGN PATENTS OR APPLlCATIONS 287,567 2/1965 Netherlands..164/282 392,785 10/1965 Switzerland ..164/282 Primary Examiner-R.Spencer Annear I Attorney-Sandoe, Hopgood & Calimafde [57] ABSTRACT In awithdrawal and straightening apparatus for continuous casting machines,banks of withdrawal and straightening rolls are mounted above and belowthe casting, the rolls of each bank being mounted in tiltable yokeswhich adjust themselves to the curvature of the casting'and distributethe loads on the rolls. The rolls of the upper bank are adjustable byhydraulic means connected to the yokes to accommodate castings ofdifferent thickness.

8 Claims, 5 Drawing Figures P'A'TENTED UECZB m2 SHEET 1 or 2 FIG.|

I N VEN TORS MAX BURKHARDT FIG?) HORST HUBER CHRISTIA CHATEA AT RNEYSPATENTED um 26 m2 SHEET 2 BF 2 INVENTORS MAX BURKHARDT T HUBER CHREQ IENCHATEAU TTORNEYS WITHDRAWAL AND STRAIGHTENING APPARATUS FOR CONTINUOUSCASTING The invention relates to a withdrawal and straighteningapparatus for continuous casting, wherein the path of the casting ischanged from a curved into a straight path between two facing banks ofrolls below and 7 above the casting.

In conventional curved type casting plants, particularly for castingslabs, the casting issuing from the curved apron is generallystraightened by using a socalled tangent roll. This roll is located in abank of rolls on the outside of the curve at the point of transitionbetween the curved and the straight path of the casting known as thetangent point. Since this roll is frequently exposed to heavy loads itsdiameter must be fairly large. However, this large diameter alsonecessitates a correspondingly wide separation from adjacent rolls ofthe bank, causing the unsupported length of the casting to be longerthan is desirable. In high speed plants, particularly in slab castingplants, the liquid crater in the casting normally extends at least intothe neighborhood of the withdrawal and straightening apparatus. A wideroll spacing, therefore, increases the risk that ferrostatic pressuremay cause bulging of the casting. In conventional plants it hastherefore become the practice to associate a larger backing roll with asmaller tangent roll. Although this enables the roll spacing to bereduced, it also entails other operating drawbacks which must beaccepted.

In practice it transpires that it is not necessarily the tangent rollthat is called upon to bear the greatest loads during straightening. Therolls preceding and following the tangent point may also function as thestraightening points and bear heavy loads. This is the case moreparticularly when colder castings are to be straightened. The result isthat rolls having design diameters that are too small may be fracturedby excessive load distributions and thereby cause expensive hold-ups.

Other difficulties arise because shrinkages occur when colder castingsare being withdrawn. As a result, loads may be applied to the withdrawaland straightening rolls in the inside bank that sometimes cause theserolls to fracture. Moreover, when withdrawing cold castings, the end ofthe casting may exert greater forces on these rolls and damage them.

It is also desirable that the withdrawal and straightening rolls apply acontact pressure to the casting that is as evenly distributed aspossible to prevent the skin of the casting from being damaged.

For precisely guiding a casting in the mold axis it is already known incontinuous casting machines of the vertical type to mount two withdrawalrolls on each side of the straight casting in a yoke and to attach theyokes to the free ends of cranked double-armed levers, whereas the otherends of the levers are in a forcelocking coupling engagement. By virtueof this arrangement a moment acting on one lever produces a contrarydeflection of the other lever, so that the contact pressure of thefacing withdrawal rolls is the same. However, this withdrawal apparatusis unsuitable for Straightening a curved casting, as obtained in curvedtype casting plants. I

In order to achieve uniform contact pressure of the withdrawal andstraightening rolls on the casting, the

rolls facing the concave side of the casting in one known withdrawal andstraightening machine are mounted in a yoke. The ends of the yoke areattached to hydraulic thrust generating devices for pressing the rollsagainst the casting. Since the rolls are mounted in a yoke that isguided on both sides and can only move in the vertical, some rolls maybe overloaded and fracture. Moreover, when the straightening conditionschange, it is not possible to adapt to the changed loading.

The object of the present invention is to provide a withdrawal andstraighteningapparatus which avoids the above-described objections,particularly roll fractures, and permits the straightening system toadapt itself to existing loading conditions even though the rolls arespaced closely together. Another object of the invention is to simplifyexisting withdrawal and straightening apparatus by utilizing standardelements and thereby reducing the cost. I

The contemplated objects are achieved by mounting at least two rolls ofat least one bank of rolls as a unit in a tiltable yoke. I

By thus mounting the rolls in a tiltable yoke they ca adapt themselvesto different loading conditions. If the dimensions of the casting aresuch that the tangent roll 7 tom outer bank of rolls in order to takefurther ad-- vantage of the compact design and favorable distribution offorces. Preferably the pivot axis of one yoke is contained in a verticalplane which contains the tangent point andthe center of curvature. It isuseful to mount two rolls in one yoke but if desired several rolls, forinstance three, may be mounted in a yoke.

In the further development of this principle two tilta ble yokes eachcarrying two rolls, for example, may themselves be mounted on a commontiltable yoke. If the pivot axis of the common yoke is in a verticalplane containing the tangent point, then the loads due to thestraightening action can be distributed evenly within a still widerrange without any individual roll being overloaded.

This principle of load distribution between several rolls also appliesto the upper bank of rolls. If uneven load distributions arise, due, forexample, to thermal stresses and the distortion of the casting during astoppage caused by a breakout of metal, then the tilting movement of ayoke carrying at least two rolls avoids damage being done to thewithdrawal and straightening rolls of the upper bank.

For lifting and lowering a yoke, as for the purpose of adjusting thewithdrawal rolls to casting cross sections of different thickness,hydraulic means are provided. By connecting the mounting of a yoke tothe piston of a hydraulic actuator, only a single hydraulic cylinder andpiston is needed on each side of the casting for adjusting all the rollsin the yoke. A special support for the upper yoke, as in plants hithertoknown, is thus rendered unnecessary. Should lateral thrusts arise, thenthese are transmitted by the yoke downwards into the supportingstructure or framework.

l060l2 mos In particular cases, as at the end of a casting operation,due to the temporary interruption needed for the formation of a cap, itis possible for the end portion of the casting to cause tilting andoverloading of individual rolls as it passes under the yoke. This can beprevented by the provision of one or more simple mechanical stops whichtake up the thrusts and transmit them into the framework. I

The number of rolls mounted in one yoke may differ butmust be at leasttwo. This is particularly important in that part of the withdrawal andstraightening apparatus which precedes. the tangent point, i.e., thatwhich is associated with the curved portion of the cast- Other detailsof the invention will be described with referen cc to embodiments shownin the drawings.

FIG. 1 is aside elevation, schematically represented of curved-typeplants provided with the proposed withdrawal and straighteningapparatus.

FIG. 2 is a side elevation of a section of the withdrawal andstraightening apparatus.

FIG. 3 is a section taken on the line'III III in FIG.

FIG. 4 is a side elevation of a different embodiment, and

FIG. 5 is a section taken on the line V V in FIG. 4.

Referring to FIG. 1 a casting 1 travels first down a curved apron 2comprising a plurality of sections curved about a center 0, and thenenters a withdrawal and straightening apparatus 3. This withdrawal andstraightening apparatus has two banks of rolls 19 and 20 on oppositesides of the casting and comprises a plurality of sections 4, 5, 6, 7,8. A selectable number of said rolls are driven and effect thewithdrawal of the casting l which, having passed through the withdrawaland straightening apparatus, continues as a straightened strand totravel along a roller bed to a point where it may be subdivided bycutting devices. At the tangent point 9, the curved path becomes.straight. In this embodiment each roll section has two rolls ll, 12 inthe upper bank 19 and two rolls ll, 12' in the lower bank 20. The pairsof rollers are mounted in tiltable yokes I5 and 16, respectively, asshown in FIGS. 2 and 3 which illustrate an individual section. The yoke15 pivots on a pin 17 and the yoke 16 pivots on a pin 18.

On each side of the casting is a hydraulic actuator comprising acylinder 21 and a piston rod 22. The cylinder is fitted into asupporting frame 23 and located therein. The pivot pin 18 is connectedby a member to the frame 23 and the pivot pin 17 is connected to apiston rod 22. This hydraulic actuator permits the two rolls 11, 12 ofthe upper bank 19 to be moved perpendicularly to the casting to adjustthe rolls to castings of different cross sections. The yoke on the pivotpin 17 permits the rollers to adapt themselves to the curvature of thecasting and the load to be evenly divided between the two rolls.

The yoke 16 containing the rolls 11, 12' in the outer bank 20 of rollslikewise provides a favorable distribution of the forces generatedduring straightening. It is desirable to dispose a section of thedescribed kind inhas several different radii of curvature this planepreferably contains the radius of curvature of the apron sectiondirectly preceding the withdrawal and straightening apparatus. Stops 27,28 are attached to the structure 23 to prevent excessive tiltingmovements of the yoke 16.

The center section shown in FIGS. 4 and S of a different embodiment ofthe withdrawal and straightening apparatus preceded and followed by twofurther sections designed as shown in FIG. 2, comprises four rolls 31,32, 33, 34 in the upper bank and 31", 32', 33', 34 in the lower bank 20of rolls, but two each of the rolls, 31, 32, 33, 34, 31, 32', 33', 34are mounted in a separate yoke 35, 36, 37, 38. The upper rockable yokes35 and 36 are each connected on each'side of the casting to a hydraulicactuator consisting of a cylinder 41, 42 and the associated piston rod.By operation of the actuators the perpendicular spacing of the two banks19, 20 of rolls can be varied. 4 I

The two bottom rockable yokes 37 and 38 are connected to the hydrauliccylinders 41, 42. Both cylinders are movable in the frame 23 andpivotably connected to the supporting'arms of a common yoke 43. The yoke43, which has a pivot axis 44 that preferably lies in a plane throughthe tangent point 9 and the center of curvature 0 normal to the castingaxis thus carries the two yokes 37 and 38 on the interposed cylinders.This arrangement enables the loads arising at the tangent point to bedistributed between four rolls permitting the diameter and spacing ofthe rolls to be further reduced. The deflectability of the yokes islimited by stops 45, 46.

Within the scope of the present invention any number of sections can beassociated on the unit construction principle so that, according to thecasting rate and the resultant crater depth, the formation of bulges canbe controlled. Particular sections comprising for instance one yokeabove and one below the casting, may be freely movable transversely ofthe casting axis and transversely of the pivot axes of the yokes, sothat the rolls of both yokes can follow the motions of the castingwithout the distance between the upper and bottom bank of rolls beingchanged.

In the same way it is possible to provide a major number of rolls, saythree rolls instead of two rolls in one yoke. Alternatively, one or moretiltable yokes may be provided in only one bank of rolls, for instancethe inner bank 19 of rolls.

It will be understood that the invention is also ap plicable to plantswith a partly curved apron.

According to requirements any desired rolls may be driven rolls. Forexample, in the embodiment illustrated in FIG. 4 the rolls 31, 32, 31',32', 33', 34', may be driven by conventional means.

We claim as our invention:

1. A withdrawal and straightening apparatus for continuous castingplants, wherein the casting is conveyed from a curved into a rectilinearpath between two facing banks of withdrawal and straightening rollsdisposed above and below the casting and defining said path,characterized in that at least two casting withdrawal and straighteningrolls adjacent each other in at least one of said two facing banks ofrolls are mounted as a unit in a tiltable yoke, said yoke having meansdefining a pivot axis for mounting said yoke to be tiltable foradjustment of said at least two withdrawal and straightening rolls tothe curvature of the casting and to safeguard against fracture of saidwithdrawal and straightening rolls due to possible roll overloadingduring the casting withdrawal and straightening operations.

2 A withdrawal and straightening apparatus according to claim 1,characterized in that at least one tiltable yoke carries rolls in thebank of rolls disposed below the casting.

3. A withdrawal and straightening apparatus for continuous castingplants, wherein the casting is conveyed from a curved into a rectilinearpath between two facing banks of rolls disposed above and below thecasting, the improvement comprising a tiltable yoke for mounting as aunit at least two rolls of at least one bank of rolls, said tiltableyoke carrying said at least two rolls of the bank of rolls disposedbelow the casting, said tiltable yoke having a pivot axis lying in avertical plane through the tangent point and the center of curvature ofthe casting.

4. A withdrawal and straightening apparatus accord ing to claim 1,characterized in that two tiltable yokes which carry rolls disposedbelow the casting are mounted on a common tiltable yoke.

5. A withdrawal and straightening apparatus for continuous castingplants, wherein the casting is conveyed from a curved into a rectilinearpath between two facing banks of rolls disposed above and below thecasting, the improvement comprising at least two tiltable yokes forcarrying rolls disposed below the casting, each of said tiltable yokeshaving mounted thereat at least two rolls of said bank of rolls disposedbelow the casting, a common tiltable yoke for mounting said two tiltableyokes, said common tiltable yoke having a pivot axis lying in a verticalplane through the tangent point and the center of curvature of thecasting.

6. A withdrawal and straightening apparatus according to claim 1,characterized in that at least one tiltable yoke which carries rolls inthe bank of rolls disposed above the casting is movable by hydraulicmeans in a direction normal to the casting axis.

7. A withdrawal and straightening apparatus according to claim 6,characterized in-that a tiltable yoke is connected on each side to ahydraulic cylinder which is guided and held in the frame.

8. A withdrawal and straightening apparatus according to claim 1,characterized in that the range of movement of the tiltable yoke islimited by stops.

1. A withdrawal and straightening apparatus for continuous castingplants, wherein the casting is conveyed from a curved into a rectilinearpath between two facing banks of withdrawal and straightening rollsdisposed above and below the casting and defining said path,characterized in that at least two casting withdrawal and straighteningrolls adjacent each other in at least one of said two facing banks ofrolls are mounted as a unit in a tiltable yoke, said yoke having meansdefining a pivot axis for mounting said yoke to be tiltable foradjustment of said at least two withdrawal and straightening rolls tothe curvature of the casting and to safeguard against fracture of saidwithdrawal and straightening rolls due to possible roll overloadingduring the casting withdrawal and straightening operations.
 3. Awithdrawal and straightening apparatus for continuous casting plants,wherein the casting is conveyed from a curved into a rectilinear pathbetween two facing banks of rolls disposed above and below the casting,the improvement comprising a tiltable yoke for mounting as a unit atleast two rolls of at least one bank of rolls, said tiltable yokecarrying said at least two rolls of the bank of rolls disposed below thecasting, said tiltable yoke having a pivot axis lying in a verticalplane through the tangent point and the center of curvature of thecasting.
 4. A withdrawal and straightening apparatus according to claim1, characterized in that two tiltable yokes which carry rolls disposedbelow the casting are mounted on a common tiltable yoke.
 5. A withdrawaland straightening apparatus for continuous casting plants, wherein thecasting is conveyed from a curved into a rectilinear path between twofacing banks of rolls disposed above and below the casting, theimprovement comprising at least two tiltable yokes for carrying rollsdisposed below the casting, each of said tiltable yokes having mountedthereat at least two rolls of said bank of rolls disposed below thecAsting, a common tiltable yoke for mounting said two tiltable yokes,said common tiltable yoke having a pivot axis lying in a vertical planethrough the tangent point and the center of curvature of the casting. 6.A withdrawal and straightening apparatus according to claim 1,characterized in that at least one tiltable yoke which carries rolls inthe bank of rolls disposed above the casting is movable by hydraulicmeans in a direction normal to the casting axis.
 7. A withdrawal andstraightening apparatus according to claim 6, characterized in that atiltable yoke is connected on each side to a hydraulic cylinder which isguided and held in the frame.
 8. A withdrawal and straighteningapparatus according to claim 1, characterized in that the range ofmovement of the tiltable yoke is limited by stops.